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authorCharan Teja Reddy <charante@codeaurora.org>2021-09-03 00:59:56 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-09-03 19:58:17 +0300
commite1e92bfa3825b72be4957f9fef267b3106d20aa6 (patch)
tree8d99328e0d396d826ba6ade4a4414b1452e6229d
parent1399af7e54896c774d67f1c1acc491b07149421d (diff)
downloadlinux-e1e92bfa3825b72be4957f9fef267b3106d20aa6.tar.xz
mm: compaction: optimize proactive compaction deferrals
Vlastimil Babka figured out that when fragmentation score didn't go down across the proactive compaction i.e. when no progress is made, next wake up for proactive compaction is deferred for 1 << COMPACT_MAX_DEFER_SHIFT, i.e. 64 times, with each wakeup interval of HPAGE_FRAG_CHECK_INTERVAL_MSEC(=500). In each of this wakeup, it just decrement 'proactive_defer' counter and goes sleep i.e. it is getting woken to just decrement a counter. The same deferral time can also achieved by simply doing the HPAGE_FRAG_CHECK_INTERVAL_MSEC << COMPACT_MAX_DEFER_SHIFT thus unnecessary wakeup of kcompact thread is avoided thus also removes the need of 'proactive_defer' thread counter. [akpm@linux-foundation.org: tweak comment] Link: https://lore.kernel.org/linux-fsdevel/88abfdb6-2c13-b5a6-5b46-742d12d1c910@suse.cz/ Link: https://lkml.kernel.org/r/1626869599-25412-1-git-send-email-charante@codeaurora.org Signed-off-by: Charan Teja Reddy <charante@codeaurora.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com> Acked-by: David Rientjes <rientjes@google.com> Cc: Nitin Gupta <nigupta@nvidia.com> Cc: Vinayak Menon <vinmenon@codeaurora.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/compaction.c29
1 files changed, 19 insertions, 10 deletions
diff --git a/mm/compaction.c b/mm/compaction.c
index 61fb64f47a06..4ee0d40d93f2 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2885,7 +2885,8 @@ static int kcompactd(void *p)
{
pg_data_t *pgdat = (pg_data_t *)p;
struct task_struct *tsk = current;
- unsigned int proactive_defer = 0;
+ long default_timeout = msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC);
+ long timeout = default_timeout;
const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
@@ -2902,23 +2903,30 @@ static int kcompactd(void *p)
trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
if (wait_event_freezable_timeout(pgdat->kcompactd_wait,
- kcompactd_work_requested(pgdat),
- msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC))) {
+ kcompactd_work_requested(pgdat), timeout)) {
psi_memstall_enter(&pflags);
kcompactd_do_work(pgdat);
psi_memstall_leave(&pflags);
+ /*
+ * Reset the timeout value. The defer timeout from
+ * proactive compaction is lost here but that is fine
+ * as the condition of the zone changing substantionally
+ * then carrying on with the previous defer interval is
+ * not useful.
+ */
+ timeout = default_timeout;
continue;
}
- /* kcompactd wait timeout */
+ /*
+ * Start the proactive work with default timeout. Based
+ * on the fragmentation score, this timeout is updated.
+ */
+ timeout = default_timeout;
if (should_proactive_compact_node(pgdat)) {
unsigned int prev_score, score;
- if (proactive_defer) {
- proactive_defer--;
- continue;
- }
prev_score = fragmentation_score_node(pgdat);
proactive_compact_node(pgdat);
score = fragmentation_score_node(pgdat);
@@ -2926,8 +2934,9 @@ static int kcompactd(void *p)
* Defer proactive compaction if the fragmentation
* score did not go down i.e. no progress made.
*/
- proactive_defer = score < prev_score ?
- 0 : 1 << COMPACT_MAX_DEFER_SHIFT;
+ if (unlikely(score >= prev_score))
+ timeout =
+ default_timeout << COMPACT_MAX_DEFER_SHIFT;
}
}